This invention relates generally to an energy system for an electronic watch which includes a primary power source whose voltage is fed to an energy converter to produce an operating voltage for the watch and also acting to charge a buffer accumulator which maintains this voltage, and more particularly to an arrangement in a watch of this type for continuously monitoring the energy system and for providing a signal indicative of its status.
Electronic watches of modern design include a high-frequency quartz crystal oscillator functioning as a frequency-standard or time base, the high-frequency output thereof being applied to a frequency divider which yields timing pulses that serve to drive a digital LCD or LED time display or to actuate the stepping motor of an analog time display.
Energy systems are known for such watches which make use of a thermoelectric generator, a solar cell or mechanically-operated means as a primary power source, the source being coupled to an energy converter in an arrangement which produces an uninterrupted operating voltage for the watch.
Thus in the case of a wristwatch equipped with thermoelectric or Peltier elements adapted to exploit the temperature gradient established between the back of the watch case which is in physical contact with the wrist of the wearer and another part of the case thermally insulated from the back, no primary power is generated when the watch is not worn on the wrist. It is for this reason, a watch using a thermoelectric generator in conjunction with an energy converter must also include a buffer accumulator capable of assuring the continuous operation of the watch should the primary source be rendered inactive.
In normal operation of a watch of this type, the voltage obtained from the energy converter is sufficient to operate the electronic circuits of the watch and the ditital or analog display thereof, and also to charge the buffer accumulator. However, should the energy converter voltage become zero or be reduced to a level insufficient to operate the watch, the buffer accumulator which then supplies the necessary operating voltage can only keep the watch going for a relatively limited period of time before it is exhausted.
An electronic watch having an energy system which relies on a buffer accumulator to maintain the operating voltage almost inevitably requires more attention than a watch powered by a replaceable battery. For this reason, information as to the existing status of the energy system would be useful to the manufacturer of the watch, as well as to watch dealers and watch users. Of particular interest in this regard is information as to whether, at any given time, the accumulator is being charged or discharged.
For example, if the watch has been strapped to the wrist of the wearer for several hours so that the primary thermoelectric power source is presumably active, information indicating that the accumulator was then discharging would indicate a defective operation; for under these circumstances the accumulator should be charging.
In electronic watches operated by an energy system of the type described, no means have heretofore been provided to indicate the operating status of the system. Thus in the case of an energy system for a watch utilizing a solar cell, since one has no information as to whether at a given time the accumulator is in a charged state, in order to prevent excessive discharge of the accumulator, the user has to depend on frequent exposure of the watch cell to light to avoid an undue discharge. Even in the case of thermoelectrically-operated watches, no means have heretofore been provided to improve the dependability of the watch by monitoring the status of the energy system.